View source for Variable Specific Impulse Magnetoplasma Rocket

{{Short description|Electrothermal thruster in development}}
{{Use mdy dates|date=February 2012}}
[[File:VASIMR spacecraft.jpg|thumb|upright=1.5|Artist's impression of a spacecraft powered by a VASIMR engine]]

The '''Variable Specific Impulse Magnetoplasma Rocket''' ('''VASIMR''') is an electrothermal thruster under development for possible use in [[spacecraft propulsion]]. It uses [[radio wave]]s to [[ionization|ionize]] and heat an [[chemically inert|inert]] [[rocket propellant|propellant]], forming a plasma, then a [[magnetic field]] to confine and accelerate the expanding [[Plasma (physics)|plasma]], generating [[thrust]]. It is a [[plasma propulsion engine]], one of several types of spacecraft [[Electrically powered spacecraft propulsion|electric propulsion]] systems.<ref name="VASIMR-Engine">{{cite web |url=http://www.adastrarocket.com/aarc/VASIMR |title=VASIMR |author=Ad Astra Rocket Company |publisher=Ad Astra Rocket Company |access-date=July 9, 2019 |archive-url=https://web.archive.org/web/20190707234837/http://www.adastrarocket.com/aarc/VASIMR |archive-date=July 7, 2019 |url-status=dead }}</ref>

The VASIMR method for heating [[plasma (physics)|plasma]] was originally developed during [[nuclear fusion]] research. VASIMR is intended to bridge the gap between high thrust, low [[specific impulse]] [[chemical rocket]]s and low thrust, high specific impulse electric propulsion, but has not yet demonstrated high thrust. The VASIMR concept originated in 1977 with former NASA astronaut [[Franklin Chang-Díaz]], who has been developing the technology ever since.<ref name="VASIMR-History">{{cite web |url=http://www.adastrarocket.com/aarc/history |title=History |author=Ad Astra Rocket Company |publisher=Ad Astra Rocket Company |access-date=July 9, 2019 }}</ref>

==Design and operation==
[[File:Plasma propulsion engine.webp|thumb|upright=1.5|3D sketch of an [[electromagnetic propulsion]] [[Plasma propulsion engine|fusion plasma]] thruster]]

VASIMR is a type of electrothermal plasma thruster/electrothermal magnetoplasma thruster. In these engines, a neutral, inert propellant is ionized and heated using radio waves. The resulting plasma is then accelerated with magnetic fields to generate thrust. Other related [[electrically powered spacecraft propulsion]] concepts are the [[electrodeless plasma thruster]], the microwave [[arcjet rocket]], and the [[pulsed inductive thruster]]. 

The propellant, a neutral gas such as [[argon]] or [[xenon]], is injected into a hollow cylinder surfaced with electromagnets. On entering the engine, the gas is first heated to a "[[cold plasma]]" by a helicon RF antenna/coupler that bombards the gas with electromagnetic energy, at a [[radio frequency|frequency]] of 10 to 50 [[megahertz|MHz]],<ref name="VASIMR Prefeasibility Analysis">{{Cite journal |title=VASIMR Prefeasibility Analysis |journal=Advanced Propulsion Systems and Technologies, Today to 2020 |page=335 |date=2008 |first=Alessandra |last=Negrotti }}</ref> stripping electrons off the propellant atoms and producing a plasma of ions and free electrons. By varying the amount of RF heating energy and plasma, VASIMR is claimed to be capable of generating either low-thrust, high–specific impulse exhaust or relatively high-thrust, low–specific impulse exhaust.<ref name="Principal VASIMR results">{{Cite conference |url=http://www.adastrarocket.com/TimSTAIF2005.pdf |title=Principal VASIMR Results and Present Objectives |conference=Space Technology and Applications International Forum - Staif 2005 |volume=746 |pages=976–982 |date=February 13–17, 2005 |author=Tim W. Glover |display-authors=etal |access-date=February 27, 2010 |bibcode=2005AIPC..746..976G |doi=10.1063/1.1867222 |archive-date=May 29, 2015 |archive-url=https://web.archive.org/web/20150529075638/http://www.adastrarocket.com/TimSTAIF2005.pdf |url-status=dead }}</ref> The second phase of the engine is a strong solenoid-configuration electromagnet that channels the ionized plasma, acting as a convergent-divergent nozzle like the physical nozzle in conventional rocket engines.

A second coupler, known as the Ion Cyclotron Heating (ICH) section, emits electromagnetic waves in resonance with the orbits of ions and electrons as they travel through the engine. Resonance is achieved through a reduction of the magnetic field in this portion of the engine that slows the orbital motion of the plasma particles. This section further heats the plasma to greater than {{cvt|1000000|K|C F}}—about 173 times the temperature of the [[Sun]]'s surface.<ref name="Air_March_2004">{{cite news|author=Beth Dickey|title=Star Power|url=http://www.airspacemag.com/space/star-power-6700758|access-date=February 7, 2014|newspaper=Air & Space, Smithsonian|date=March 2004}}</ref>

The path of ions and electrons through the engine approximates lines parallel to the engine walls; however, the particles actually orbit those lines while traveling linearly through the engine. The final, diverging, section of the engine contains an expanding magnetic field that ejects the ions and electrons from the engine at velocities as great as {{cvt|50000|m/s|km/h}}.<ref name="Principal VASIMR results"/><ref name="VASIMR-Technology">{{cite web |url=http://www.adastrarocket.com/aarc/Technology |title=Technology |date=2009 |author=Ad Astra Rocket Company |publisher=Ad Astra Rocket Company |access-date=December 10, 2012 |archive-date=May 22, 2013 |archive-url=https://web.archive.org/web/20130522003114/http://www.adastrarocket.com/aarc/Technology |url-status=dead }}</ref>

===Advantages===
In contrast to the typical [[Electron cyclotron resonance|cyclotron resonance]] heating processes, VASIMR ions are immediately ejected from the magnetic nozzle before they achieve [[Thermalisation|thermalized distribution]]. Based on novel theoretical work in 2004 by Alexey V. Arefiev and Boris N. Breizman of [[University of Texas at Austin]], virtually all of the energy in the ion [[cyclotron]] wave is uniformly transferred to ionized plasma in a single-pass cyclotron absorption process. This allows for ions to leave the magnetic nozzle with a very narrow energy distribution, and for significantly simplified and compact magnet arrangement in the engine.<ref name="Principal VASIMR results" />

VASIMR does not use electrodes; instead, it magnetically shields plasma from most hardware parts, thus eliminating electrode erosion, a major source of wear in ion engines.<ref name="Engine_2003">{{cite web|display-authors=7|first1=Jared P. |last1=Squire|first2=Franklin R. |last2=Chang-Díaz |author2-link=Franklin Chang-Díaz |first3=Verlin T. |last3=Jacobson |first4=Tim W. |last4=Glover |first5=F. Wally |last5=Baity |first6=Richard H. |last6=Goulding |first7=Roger |last7=Bengtson |first8=Edgar A. |last8=Bering |first9=Kristy A. |last9=Stokke|name-list-style=amp|title=EXPERIMENTAL RESEARCH PROGRESS TOWARD THE VASIMR ENGINE|url=http://spaceflight.nasa.gov/shuttle/support/researching/aspl/reference/iepc03.pdf|website=28th International Electric Propulsion Conference, Toulouse, France, 17–21 March 2003|publisher=28th International Electric Propulsion Conference|access-date=February 7, 2014|archive-date=August 1, 2014|archive-url=https://web.archive.org/web/20140801011106/http://spaceflight.nasa.gov/shuttle/support/researching/aspl/reference/iepc03.pdf|url-status=dead}}</ref> Compared to traditional rocket engines with very complex plumbing, high performance valves, actuators and turbopumps, VASIMR has almost no moving parts (apart from minor ones, like gas valves), maximizing long term durability.<ref>{{cite report|title=VASIMR Engine|first=Kipp |last=Larson|publisher=University of Colorado - Boulder |url=https://www.colorado.edu/faculty/kantha/sites/default/files/attached-files/may_3_2016_1045_pm_-_final_project_larson.pdf |date=May 2016|access-date=April 2, 2023}}</ref>

===Disadvantages===
According to Ad Astra as of 2015, the VX-200 engine requires 200&nbsp;kW electrical power to produce {{Nowrap|5 N}} of thrust, or 40&nbsp;kW/N.<ref name="VASIMR-Technology"/> In contrast, the conventional [[NEXT (ion thruster)|NEXT ion thruster]] produces 0.327 N with only 7.7&nbsp;kW, or 24&nbsp;kW/N.<ref name="VASIMR-Technology"/> Electrically speaking, NEXT is almost twice as efficient, and successfully completed a 48,000 hours (5.5 years) test in December 2009.<ref name="test">{{cite web| url=http://www.nasa.gov/home/hqnews/2013/jun/HQ_13-193_Ion_Thruster_Record.html | title= NASA Thruster Achieves World-Record 5+ Years of Operation | author1=Dwayne Brown | author2=Katherine K. Martin | author3= Glenn Mahone |access-date=2013-06-24}}</ref><ref>{{cite web| url=http://www.nasa.gov/content/next-provides-lasting-propulsion-and-high-speeds-for-deep-space-missions/index.html | title= NEXT Provides Lasting Propulsion and High Speeds for Deep Space Missions | author1= Nancy Smith Kilkenny|access-date=29 September 2013}}</ref>

New problems also emerge with VASIMR, such as interaction with strong magnetic fields and thermal management. The inefficiency with which VASIMR operates generates substantial [[waste heat]] that needs to be channeled away without creating thermal overload and thermal stress. The [[superconducting magnet|superconducting electromagnets]] necessary to contain hot plasma generate [[Tesla (unit)|tesla]]-range magnetic fields<ref name="VASIMR Exceeding 50kW">{{cite web |url=http://www.adastrarocket.com/ISGLP_JPSquire2008.pdf |title=VASIMR Performance Measurements at Powers Exceeding 50 kW and Lunar Robotic Mission Applications |date=September 5–6, 2008 |author=Jared P. Squire |display-authors=etal |publisher=International Interdisciplinary Symposium on Gaseous and Liquid Plasmas |access-date=February 27, 2010 |archive-date=February 26, 2015 |archive-url=https://web.archive.org/web/20150226072105/http://www.adastrarocket.com/ISGLP_JPSquire2008.pdf |url-status=dead }}</ref> that can cause problems with other onboard devices and produce unwanted torque by interaction with the [[magnetosphere]]. To counter this latter effect, two thruster units can be packaged with magnetic fields oriented in opposite directions, making a net zero-torque magnetic [[quadrupole]].<ref name="aarc20110208">{{cite web |title=International Space Station Mission |url=http://www.adastrarocket.com/aarc/VASIMRISS |publisher=Ad Astra Rocket Company |access-date=February 8, 2011 |date=2011 |quote=The VX-200 will provide the critical data set to build the VF-200-1, the first flight unit, to be tested in space aboard the International Space Station (ISS). The electrical energy will come from ISS at low power level, be stored in batteries and used to fire the engine at 200 kW. |url-status=dead |archive-url=https://web.archive.org/web/20110315070521/http://www.adastrarocket.com/aarc/VASIMRISS |archive-date=March 15, 2011 |df=mdy-all }}</ref>

==Research and development==
[[File:Vasimr.png|thumb|upright=1.5|VASIMR laboratory experiment schematic]]

The first VASIMR experiment was conducted at [[Massachusetts Institute of Technology]] in 1983. Important refinements were introduced in the 1990s, including the use of the helicon plasma source, which replaced the plasma gun originally envisioned and its electrodes, adding to durability and long life.<ref>{{cite web|title=VASIMR (Variable Specific Impulse Magnetoplasma Rocket)|date=Jul 28, 2021|url=https://www.eoportal.org/other-space-activities/vasimr|website=eoportal.org|access-date=April 2, 2023}}</ref>

{{As of|2010|post=,}} [[Ad Astra Rocket Company]] (AARC) was responsible for VASIMR development, signing the first [[Space Act Agreement]] on 23 June 2005 to privatize VASIMR technology. Franklin Chang-Díaz is Ad Astra's chairman and CEO, and the company had a testing facility in [[Liberia, Costa Rica]] on the campus of [[EARTH University|Earth University]].<ref name="summary">{{cite web |url=http://www.adastrarocket.com/EXECUTIVE%20SUMMARY240110.pdf |title=Executive summary |date=January 24, 2010 |publisher=Ad Astra Rocket Company |access-date=February 27, 2010 |url-status=dead |archive-url=https://web.archive.org/web/20100331171616/http://www.adastrarocket.com/EXECUTIVE%20SUMMARY240110.pdf |archive-date=March 31, 2010 |df=mdy-all }}</ref>

===VX-10 to VX-50===
[[File:VASIMR test.jpg|thumb|upright=1.5|VX-10 test chamber at the Advanced Space Propulsion Laboratory, [[Johnson Space Center]]]]

In 1998, the first helicon plasma experiment was performed at the [[Johnson Space Center#Advanced Space Propulsion Laboratory|ASPL]]. VASIMR experiment 10 (VX-10) in 1998 achieved a helicon RF plasma discharge of up to 10&nbsp;kW and VX-25 in 2002 of up to 25&nbsp;kW. By 2005 progress at ASPL included full and efficient plasma production and acceleration of the plasma ions with the 50&nbsp;kW, {{convert|0.5|N|lbf|1}} thrust VX-50.<ref name="Principal VASIMR results" /> Published data on the 50&nbsp;kW VX-50 showed the electrical efficiency to be 59% based on a 90% coupling efficiency and a 65% ion speed boosting efficiency.<ref name="IEPC-2007-181">{{cite web |url=http://www.adastrarocket.com/Jared_IEPC07.pdf |title=High Power VASIMR Experiments using Deuterium, Neon and Argon |date=September 17–20, 2007 |first1=Jared P |last1=Squire |display-authors=etal |publisher=International Electric Propulsion Conference 2007 |access-date=February 27, 2010 |archive-date=February 26, 2015 |archive-url=https://web.archive.org/web/20150226072114/http://www.adastrarocket.com/Jared_IEPC07.pdf |url-status=dead }}</ref>{{failed verification|date=April 2021}}

===VX-100===
The 100 kilowatt VASIMR experiment was successfully running by 2007 and demonstrated efficient plasma production with an ionization cost below 100{{nbsp}}eV.<ref name=PR_June_2007>{{cite web|title=Ad Astra's VX-100 test bed achieves record plasma performance|url=http://www.adastrarocket.com/AdAstraPressRelease061207-1.pdf|website=PRESS RELEASE 061207, June 12, 2007|publisher=Ad Astra|access-date=February 7, 2014|archive-date=October 30, 2012|archive-url=https://web.archive.org/web/20121030190312/http://www.adastrarocket.com/AdAstraPressRelease061207-1.pdf|url-status=dead}}</ref> VX-100 plasma output tripled the prior record of the VX-50.<ref name=PR_June_2007/>

The VX-100 was expected to have an ion speed boosting efficiency of 80%, but could not achieve this efficiency due to losses from the conversion of DC electric current to radio frequency power and the auxiliary equipment for the superconducting magnet.<ref name="IEPC-2007-181"/><ref name="whitepaper">{{cite web |url=http://www.adastrarocket.com/AIAA2006.pdf |title=Recent Improvements In Ionization Costs And Ion Cyclotron Heating Efficiency In The VASIMR Engine |date=January 9–12, 2006 |first1=Edgar A |last1=Bering |display-authors=etal |publisher=AIAA Aerospace Sciences Meeting and Exhibit |access-date=February 27, 2010 |archive-date=January 19, 2016 |archive-url=https://web.archive.org/web/20160119120839/http://www.adastrarocket.com/AIAA2006.pdf |url-status=dead }}</ref> In contrast, 2009 state-of-the-art, proven ion engine designs such as NASA's [[High Power Electric Propulsion]] (HiPEP) operated at 80% total thruster/[[power processing unit|PPU]] [[Efficient energy use|energy efficiency]].<ref name="NASA report">{{cite journal |url=https://arc.aiaa.org/doi/10.2514/6.2004-3453|title=An Overview of the High Power Electric Propulsion (HiPEP) Project |date=July 14, 2004|first1=Frederick W |last1=Elliott |display-authors=etal |journal=AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit |doi=10.2514/6.2004-3453 |isbn=978-1-62410-037-6 |access-date=April 2, 2023|url-access=subscription }}</ref>

===VX-200===
[[File:VX-200 operation full power.jpg|thumb|upright=1.5|VX-200 plasma engine at full power, employing both stages with full magnetic field]]
On 24 October 2008, the company announced in a press release that the [[Helicon (physics)|helicon]] plasma generation component of the 200&nbsp;kW VX-200 engine had reached operational status. The key enabling technology, solid-state DC-RF power-processing, reached 98% efficiency. The helicon discharge used 30&nbsp;kW of radio waves to turn [[argon]] gas into plasma. The remaining 170&nbsp;kW of power was allocated for acceleration of plasma in the second part of the engine, via ion cyclotron resonance heating.<ref name="VASIMR VX-200 first stage">{{cite press release |url=http://www.adastrarocket.com/Release241008.pdf |title=VASIMR VX-200 first stage achieves full power rating |publisher=Ad Astra Rocket Company |date=October 24, 2008 |access-date=February 27, 2010 |archive-date=November 5, 2015 |archive-url=https://web.archive.org/web/20151105185042/http://www.adastrarocket.com/Release241008.pdf |url-status=dead }}</ref>

Based on data from VX-100 testing,<ref name="VASIMR Exceeding 50kW"/> it was expected that, if room temperature superconductors are ever discovered, the VX-200 engine would have a system efficiency of 60–65% and a potential thrust level of 5&nbsp;N. Optimal [[specific impulse]] appeared to be around 5,000&nbsp;s using low cost argon propellant. One of the remaining untested issues was whether the hot plasma actually detached from the rocket. Another issue was waste heat management. About 60% of input energy became useful kinetic energy. Much of the remaining 40% is secondary ionizations from plasma crossing magnetic field lines and exhaust divergence. A significant portion of that 40% was waste heat (see [[energy conversion efficiency]]). Managing and rejecting that waste heat is critical.<ref>{{cite journal |title=A review of the processing, composition, and temperature-dependent mechanical and thermal properties of dielectric technical ceramics |journal=Journal of Materials Science |volume = 47|issue=10 |pages=4211–4235 |first1=Daithí |last1=de Faoite |first2=David J. |last2=Browne |first3=Franklin R. |last3=Chang-Díaz |author3-link=Franklin Chang-Díaz |first4=Kenneth T. |last4=Stanton |date=November 17, 2011 |doi=10.1007/s10853-011-6140-1|bibcode = 2012JMatS..47.4211F |hdl=10197/8477 |s2cid=137329155 |hdl-access=free }}</ref>

Between April and September 2009, 200&nbsp;kW tests were performed on the VX-200 prototype with 2 [[Tesla (unit)|tesla]] superconducting magnets that are powered separately and not accounted for in any "efficiency" calculations.<ref>{{cite press release |url=http://www.adastrarocket.com/Release_200kW_01Oct2009Final.pdf |title=VASIMR VX-200 reaches 200&nbsp;kW power milestone |publisher=Ad Astra Rocket Company |date=September 30, 2011 |access-date=February 24, 2012 |archive-date=March 1, 2012 |archive-url=https://web.archive.org/web/20120301192252/http://www.adastrarocket.com/Release_200kW_01Oct2009Final.pdf |url-status=dead }}</ref> During November 2010, long duration, full power firing tests were performed, reaching steady state operation for 25 seconds and validating basic design characteristics.<ref name="VASIMR VX-200 firing for 25 seconds">{{cite web |url=https://www.youtube.com/watch?v=BRS26DcQhq0  |archive-url=https://ghostarchive.org/varchive/youtube/20211211/BRS26DcQhq0| archive-date=2021-12-11 |url-status=live|title=Video of VASIMR VX-200 firing for 25 seconds at full power rating |date=December 15, 2010 |author=Benwl |publisher=Ad Astra Rocket Company |access-date=January 4, 2011}}{{cbignore}}</ref>

Results presented in January 2011 confirmed that the design point for optimal efficiency on the VX-200 is 50&nbsp;km/s exhaust velocity, or an [[specific impulse|''I''{{sub|sp}}]] of 5000{{nbsp}}s. The 200&nbsp;kW VX-200 had executed more than 10,000 engine firings with [[argon]] propellant at full power by 2013, demonstrating greater than 70% thruster efficiency relative to RF power input.<ref name=ilin2013>{{cite conference |url=http://www.adastrarocket.com/AndrewIEPC13-336-Paper.pdf |title=VASIMR Solar Powered Missions for NEA Retrieval and NEA Deflection |conference=33rd International Electric Propulsion Conference. October 6–10, 2013. Washington, D.C. |first1=Andrew V. |last1=Ilin |first2=Daniel A. |last2=Gilman |first3=Mark D. |last3=Carter |first4=Franklin R. |last4=Chang-Díaz |author4-link=Franklin Chang-Díaz |first5=Jared P. |last5=Squire |first6=Joseph E. |last6=Farrias |date=2013 |id=IEPC-2013-336 |access-date=May 14, 2014 |archive-date=May 14, 2014 |archive-url=https://web.archive.org/web/20140514181304/http://www.adastrarocket.com/AndrewIEPC13-336-Paper.pdf |url-status=dead }}</ref>

====VX-200SS====
In March 2015, Ad Astra announced a $10 million award from NASA to advance the technology readiness of the next version of the VASIMR engine, the '''VX-200SS''' to meet the needs of deep space missions.<ref>{{cite press release |url=https://www.nasa.gov/press/2015/march/nasa-announces-new-partnerships-with-us-industry-for-key-deep-space-capabilities/ |title=NASA Announces New Partnerships with U.S. Industry for Key Deep-Space Capabilities |publisher=NASA |date=March 30, 2015 |access-date=July 24, 2021}}</ref> The SS in the name stands for "steady state", as a goal of the long duration test is to demonstrate continuous operation at thermal steady state.<ref>{{cite press release |url=https://adastrarocket.com/AdAstraRelease033115final.pdf |title=Ad Astra Rocket Company wins major NASA advanced propulsion contract |publisher=Ad Astra Rocket Company |date=March 31, 2015 |access-date=July 24, 2021 |archive-date=July 24, 2021 |archive-url=https://web.archive.org/web/20210724083602/https://adastrarocket.com/AdAstraRelease033115final.pdf |url-status=dead }}</ref>

In August 2016, Ad Astra announced completion of the milestones for the first year of its 3-year contract with NASA. This allowed for first high-power plasma firings of the engines, with a stated goal to reach 100{{nbsp}}hr and 100&nbsp;kW by mid-2018.<ref>{{cite press release |url=https://adastrarocket.com/pressReleases/AdAstra-Release-080316-final.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://adastrarocket.com/pressReleases/AdAstra-Release-080316-final.pdf |archive-date=2022-10-09 |url-status=live |title=Ad Astra Rocket Company successfully completes all NASA NextStep Contract Milestones for year one, receives NASA approval to proceed with year two |publisher=Ad Astra Rocket Company |date=August 3, 2016 |access-date=July 24, 2021}}</ref> In August 2017, the company reported completing its Year 2 milestones for the VASIMR electric plasma rocket engine. NASA gave approval for Ad Astra to proceed with Year 3 after reviewing completion of a 10-hour cumulative test of the VX-200SS engine at 100{{nbsp}}kW. It appears as though the planned 200&nbsp;kW design is being run at 100&nbsp;kW for reasons that are not mentioned in the press release.<ref name="Ad_Astra_20170809">{{cite press release |url=https://adastrarocket.com/pressReleases/AdAstraRelease080917-final.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://adastrarocket.com/pressReleases/AdAstraRelease080917-final.pdf |archive-date=2022-10-09 |url-status=live |title=Ad Astra Rocket Company successfully completes all NASA NextStep Contract Milestones for year two, receives NASA approval to proceed with year three |publisher=Ad Astra Rocket Company |date=August 9, 2017 |access-date=August 9, 2017}}</ref> 
	 
In August 2019, Ad Astra announced the successful completion of tests of a new generation radio-frequency ([[RF]]) Power Processing Unit (PPU) for the VASIMR engine, built by [[Aethera Technologies]] Ltd. of Canada.<ref>{{cite press release |url=https://www.adastrarocket.com/pressReleases/2019/20190820-AdAstra-Aethera.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://www.adastrarocket.com/pressReleases/2019/20190820-AdAstra-Aethera.pdf |archive-date=2022-10-09 |url-status=live |title=Aethera's New RF Power Processing Unit for the VASIMR Engine Successfully Completes Full Power Vacuum and Magnetic Field Tests at Ad Astra Rocket Company's Texas Facility |publisher=Ad Astra Rocket Company |date=August 20, 2019 |access-date=July 24, 2021}}</ref> Ad Astra declared a power of 120 [[kW]] and >97% electrical-to-RF power efficiency, and that, at 52&nbsp;kg, the new RF PPU is about 10x lighter than the PPUs of competing electric thrusters ([[power-to-weight ratio]]: 2.31&nbsp;kW/kg)

In July 2021, Ad Astra announced the completion of a record-breaking test for the engine, running it for 28 hours at a power level of 82.5{{nbsp}}kW.<ref>{{cite press release |url=https://www.adastrarocket.com/pressReleases/2021/20210709-PressRelease.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://www.adastrarocket.com/pressReleases/2021/20210709-PressRelease.pdf |archive-date=2022-10-09 |url-status=live |title=Ad Astra Rocket Company shatters power and endurance record in recent tests of the VASIMR VX-200SS plasma rocket |publisher=Ad Astra Rocket Company |date=July 9, 2021 |access-date=July 15, 2021}}</ref> A second test, conducted from July 12 to 16, successfully ran the engine for 88 hours at a power level of 80{{nbsp}}kW.<ref>{{cite press release |url=https://www.adastrarocket.com/pressReleases/2021/20210722-PressRelease.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://www.adastrarocket.com/pressReleases/2021/20210722-PressRelease.pdf |archive-date=2022-10-09 |url-status=live |title=VASIMR VX-200SS plasma rocket completes record 88-hour high power endurance test |publisher=Ad Astra Rocket Company |date=July 22, 2021 |access-date=July 24, 2021}}</ref> Ad Astra anticipates conducting 100{{nbsp}}kW power level tests in 2023.<ref>{{cite news |url=https://ticotimes.net/2023/02/10/franklin-chang-diaz-talks-about-hydrogen-vasimr-artemis-and-the-costa-rica-space-agency |title=Franklin Chang-Díaz discusses Hydrogen, VASIMR, Artemis, and Costa Rica Space Agency |date=February 10, 2023 }}</ref>

==Potential applications==
VASIMR has a comparatively poor thrust-to-weight ratio, and requires an ambient vacuum.

Proposed applications for VASIMR such as the rapid transportation of people to Mars would require a very high power, low mass energy source, ten times more efficient than a nuclear reactor (see [[nuclear electric rocket]]). In 2010 NASA Administrator [[Charles Bolden]] said that VASIMR technology could be the breakthrough technology that would reduce the travel time on a Mars mission from 2.5 years to 5 months.<ref name='Morring'>{{cite journal|last1=Morring |first1=Frank |date=2010 |title=Commercial Route |journal=Aviation Week & Space Technology |volume=172 |issue=6 |pages=20–23 }}</ref> However this claim has not been repeated in the last decade.

In August 2008, Tim Glover, Ad Astra director of development, publicly stated that the first expected application of VASIMR engine is "hauling things [non-human cargo] from low-Earth orbit to low-lunar orbit" supporting NASA's return to Moon efforts.<ref name="Discovery News">{{cite web |url=http://dsc.discovery.com/news/2008/08/07/plasma-rocket.html |title=Plasma Rocket May Be Tested at Space Station |date=August 7, 2008 |author=Irene Klotz |publisher=Discovery News |access-date=February 27, 2010 }}</ref>

===Mars in 39 days===
In order to conduct an imagined crewed trip to Mars in 39 days,<ref>Video: "[https://www.youtube.com/watch?v=-nyepvfuHho Mars in 39 Days?: the VASIMR Plasma Engine. Franklin Chang-Díaz, Ph.D.]"</ref> the VASIMR would require a very high electrical power level.

On top of that, any power generation technology will produce waste heat. The necessary 200 [[megawatt]] reactor "with a power-to-mass density of 1,000 [[watt]]s per [[kilogram]]" would require extremely efficient radiators to avoid the need for "football-field sized radiators".<ref>Video: [https://www.youtube.com/watch?v=myYs4DCCZts#t=870s ''VASIMR Debate/The VASIMR Hoax – Dr. Robert Zubrin – 14th International Mars Society Convention'', Time Index 14:30]</ref>

==See also==
* [[Comparison of orbital rocket engines]]

===Electric propulsion===
* [[Helicon Double Layer Thruster]]
* [[Magnetoplasmadynamic thruster]]
* [[Nano-particle field extraction thruster]]
* [[Pulsed plasma thruster]]

===Space fission reactors===
* [[Project Prometheus]]
* [[Safe Affordable Fission Engine]]
* [[Systems for Nuclear Auxiliary Power]]
* [[TOPAZ nuclear reactor]]

==References==
{{Reflist}}

==Further reading==
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{{Refbegin}}
* {{Cite press release |url=http://www.nasa.gov/centers/johnson/news/releases/2006/J06-009.html |title=Agreement to Commercialize Advanced NASA Rocket Concept; Former Astronaut Franklin Chang-Díaz to Lead Effort |publisher=Johnson Space Center |date=January 23, 2006 |access-date=January 18, 2008 |id=J06-009}}
* {{Cite news |url=http://www.technologyreview.com/Infotech/19427/ |title=Rocket scientist Franklin Chang-Díaz talks about finding the power and propulsion required to colonize space |first=Erica |last=Naone |work=Technology Review |date=September 25, 2007 |access-date=February 27, 2010 |archive-date=April 4, 2012 |archive-url=https://web.archive.org/web/20120404125457/http://www.technologyreview.com/Infotech/19427/ |url-status=dead }}
* {{Cite web |url=http://www.spectrum.ieee.org/aerospace/space-flight/rockets-for-the-red-planet/0 |title=Rockets for the Red Planet |website=IEEE Spectrum |first=Sandra |last=Upson |date=June 2009 |access-date=February 27, 2010 |archive-url=https://web.archive.org/web/20110722082634/http://spectrum.ieee.org/aerospace/space-flight/rockets-for-the-red-planet/0 |archive-date=July 22, 2011 |url-status=dead |df=mdy-all }}
{{Refend}}

==External links==
{{Commons category|VASIMR}}
* [http://science.discovery.com/videos/brink-package-plasma-rocket.html "Plasma Rocket"] (Video). ''Brink''. [[Science (TV channel)|Science]]. December 18, 2008.

===NASA documents===
* [http://www.techbriefs.com/content/view/1768/32/1/0/ Variable-Specific-Impulse Magnetoplasma Rocket (Tech Brief)]
* [http://spaceflight.nasa.gov/shuttle/support/researching/aspl/vasimr.html Advanced Space Propulsion Laboratory: VASIMR]
* [http://www.nasa.gov/vision/space/travelinginspace/future_propulsion.html Propulsion Systems of the Future]

{{Spacecraft propulsion}}
{{Emerging technologies|topics=yes|space=yes}}

[[Category:Ion engines]]
[[Category:Magnetic propulsion devices]]
[[Category:Plasma technology and applications]]
[[Category:Rocket propulsion]]